Allen-Bradley 1734-SSI, User Manual, Page: 27 / 48

Rockwell Automation Publication 1734-UM007E-EN-P - October 2015 27
Chapter
4
Set and Operate Your Module
About This Chapter
Read this chapter for information about setup and operation of your module.
You need to alter the 1734-SSI module configuration, special data latch feature,
and comparator feature in order for the 1734-SSI module to operate properly
with your SSI sensor.
To quickly configure the 1734-SSI module for use with your SSI sensor, change
only the following values if they are different from the module default values:
•
Data type
•
SSI word length
•
Data rate
•
SSI word delay
Module Configuration Value
Definitions
Value Definition
RUN The SSI clock output to the SSI sensor can be turned ON or OFF by changing the RUN
setting. You may find this feature useful during machine setup or maintenance. The
default setting for RUN is ON.
When you first apply power to the module, the SSI clock output is active. The green
LED on the front of the module indicates the RUN status, as well as Bit 1 or Byte 0 in
the module status word (produced byte 8, Bit 1; 1 = RUN ON, 0 = RUN OFF).
Data Type This refers to the code type of your SSI sensor. The 1734-SSI module supports Gray and
Binary code types. The module default is Gray.
You must have the right code type selected so that other module features operate
correctly.
SSI Word Length The number of bits in a single SSI word is completely determined by the SSI sensor.
See the manufacturer’s data sheet for the sensor output word size. The word length
setting range is 2…31 bits. The default SSI word length is 13 bits.
Data Rate The data rate is the SSI sensor’s communication rate (bits/s) stated in the
manufacturer’s data sheet. The data rate you select at the SSI module equals the
approximate frequency of the SSI module’s clock output (the actual measure
frequency varies with the SSI word delay time).
The maximum data rate that can be used for your application is limited by the
transmission line length between the SSI module and sensor. See the SSI sensor data
sheet, as well as the 1734-SSI Installation Instructions, publication
1734-IN581 , for
communication rate versus transmission line length information.
The module supports the following SSI data rates: 125, 250, 500 Kbps, 1 and 2 MBps.
The module default rate is 125 Kbps.
Gray-to-Binary Conversion The 1734-SSI module can change the displayed SSI sensor data from Gray to Binary.
Change this setting to ON only when using a Gray-code sensor and you wish to read a
present SSI value that is proportional to total sensor travel.
Gray-code sensor values continuously increase and decrease as the sensor travels in
one direction, and do not provide a sense of proportionality. The module default for
this setting is OFF.